Missense mutations in LRRK2 account for between 1 and 5% of late onset PD cases in most Caucasian populations. The role of LRRK2 in idiopathic PD remains unclear, although better understanding of the signaling and physiology behind mutations in LRRK2 may help clarify pathogenic mechanisms in PD. Several lines of evidence implicate neuroinflammation in the pathogenesis of PD. While the role of LRRK2 remains unclear, several lines of evidence point to LRRK2 being involved in the innate immune response. Recent data show that LRRK2 expression and kinase activity are necessary for a full TLR4-induced pro- inflammatory response in microglia. Inflammatory markers as well as selective death of dopaminergic neurons in the substantia nigra caused by rAAV2-alpha-synuclein over-expression recapitulate aspects of PD. We hypothesize that LRRK2 may modify alpha-synuclein driven neuroinflammation, where G2019S LRRK2 exaggerates pro-inflammatory responses and LRRK2 inhibition down-regulates pro-inflammatory responses. These hypotheses will be tested in two aims: The first aim will determine whether alpha-synuclein signals through LRRK2 in primary microglia to elicit pro-inflammatory responses. Using primary microglia derived from transgenic, knockout, and control mice, the cytokine/chemokine/growth-factor response to alpha-synuclein and other pro-inflammatory stimuli will be examined. Additionally, the antigen processing/presentation capabilities of primary microglia harboring LRRK2 mutations will be examined. The second aim will determine whether LRRK2 activity and expression is necessary for rAAV2-alpha-synuclein induced inflammation and neurodegeneration, and whether G2019S-LRRK2 exacerbates neurodegeneration in the substantia nigra. Using the same animals as in aim 1, the second aim will utilize quantitative endpoints including unbiased stereological estimations of dopaminergic neurons in the substantia nigra, microglial activation, peripheral immune cell invasion, and microglia presenting antigen and inducing T-cell proliferation. Additionally, microglial polarization and activation wil be analyzed with flow cytometry. Overall, we expect to observe that G2019S LRRK2 exacerbates neurodegeneration, microglial activation, pro-inflammatory cytokine release, antigen processing/presentation, and polarization of microglia to an M1 phenotype while the knockout shows the opposite effect. The proposed training plan is sponsored by Dr. Andrew West and co-sponsored by Dr. David Standaert. Included in the training plan are experiences to help the PI gain a wide range of molecular and cellular neuroimmunology techniques, presentation of data in a written and oral format, responsibly conduct in research, and development into an independent researcher capable of carrying out high impact translation research.